Pulse dynamics in an actively mode-locked laser

John B. Geddes, William J. Firth, Kelly Black

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


We consider pulse formation dynamics in an actively mode-locked laser. We show that an amplitude-modulated laser is subject to large transient growth and we demonstrate that at threshold the transient growth is precisely the Petermann excess noise factor for a laser governed by a nonnormal operator. We also demonstrate an exact reduction from the governing PDEs to a low-dimensional system of ODEs for the parameters of an evolving pulse. A linearized version of these equations allows us to find analytical expressions for the transient growth below threshold. We also show that the nonlinear system collapses onto an appropriate fixed point, and thus in the absence of noise the ground-mode laser pulse is stable. We demonstrate numerically that, in the presence of a continuous noise source, however, the laser destabilizes and pulses are repeatedly created and annihilated.
Original languageEnglish
Pages (from-to)647-671
Number of pages24
JournalSIAM Journal on Applied Dynamical Systems
Issue number4
Publication statusPublished - 2003


  • mode-locked laser
  • transient growth
  • excess noise
  • hermite polynomials
  • photonics
  • optics


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